1. Field of the Invention
The present invention relates to a toner supply control mechanism of the electrophotographic apparatus, and more particularly relates to a toner supply control mechanism thereof.
2. Description of the Related Art
FIG. 8 is a schematic illustration showing an arrangement of the electrophotographic apparatus of the prior art, wherein the apparatus relating to toner supply and toner consumption is schematically illustrated in the drawing. The process will be explained as follows.
A toner bottle 2, which is a container charged with toner 1 functioning as powder ink, is attached to a toner supply port 3. Toner 1 is conveyed from the toner supply port 3 to a toner hopper 4 when a toner supply drive unit 5 is driven. Supply of toner from the outside of the apparatus into the toner hopper 4 will be referred to as toner supply, hereinafter. In this way, toner 1 is supplied from the outside into the apparatus. In general, toner supply indicates this operation.
When a toner supply switch 6 is pressed, the toner supply drive unit 5 is driven. When the toner supply switch 6 is pressed again during the driving operation, or alternatively when a predetermined period of time has passed, the driving operation of the toner supply drive unit 5 is stopped. The toner hopper 4 is a container in which toner 1 is stored. Inside the toner hopper 4, there is provided a toner empty sensor 7, and the shortage of toner 1 in the toner hopper 4 is detected by the toner empty sensor 7.
A toner feed drive unit 8 conveys toner 1 from the toner hopper 4 to a developing unit 9. Supply of toner from the toner hopper 4 to the developing unit 9 will be referred to as toner feed, hereinafter. Toner 1 and carrier 10, which is triboelectrically charged when it is rubbed against toner 1, are mixed with each other at a predetermined ratio, which will be referred to as a toner concentration, hereinafter. The thus obtained developer 11 is conveyed to a photoreceptor drum 12 by a development roller 13 mounted on the developing unit 9. In this way, an image on the photoreceptor drum 12 having photoconductivity is developed by toner 1. When the printing operation is conducted, toner 1 contained in developer 11 is consumed. In order to control the toner concentration to be constant, toner 1 stored in the toner hopper 4 is fed to the developing unit 9.
With reference to the timing chart shown in FIG. 7, toner supply conducted in the electrophotographic apparatus of the prior art will be described below.
When the toner empty sensor 23 detects the shortage of toner, a high level signal is outputted. In the case where the print signal 21 showing that the printing operation is being conducted is on a high level, a period of time in which the toner empty sensor signal 23 continues to be on a high level is measured by the control section. After a period of time of TO has passed, the control section judges that toner is in short supply, so that the toner shortage signal 24 becomes a high level. With this as a turning point, the printing operation is stopped and prohibited.
At this time, the print signal 21 for stopping the printing operation becomes a low level. The print prohibition signal 22 becomes a high level which shows that the printing is prohibited. At the same time, due to the high level of the toner shortage signal 24, toner shortage is reported to the outside. The operator receives the toner shortage signal 24 and attaches the toner bottle to the apparatus. Then the operator presses the toner supply switch, so that the signal becomes a high level. When the operator stops pressing the toner supply switch, the signal becomes a low level. When the toner supply switch signal 26 is turned from a high level to a low level, the toner supply signal 27 becomes a high level, and the toner supply is started. When a period of time S2 has passed from the start, the toner supply is stopped. Alternatively, when the toner supply switch is pressed, the toner supply can be stopped. When the toner shortage signal 24 showing that the toner is in short supply is on a high level, or alternatively, when the toner supply signal 27 showing that the toner is being supplied is on a high level, the print prohibition signal 22 becomes a high level, and the printing is prohibited.
When the toner is supplied, the toner empty sensor signal 23 becomes a low level. Together with the solution of toner shortage, the toner shortage signal 24 becomes a low level. After the completion of toner supply, the toner supply signal 27 becomes a low level. Then the print prohibition signal 22 becomes a low level, so that the printing is permitted. Since the operator recognizes that the printing has been permitted, he sets the print signal 21 at a high level so as to start the next printing operation.
Toner supply of the electrophotographic apparatus of the prior art described above is conducted by the operator when he has received the toner shortage signal. In order to extend a period in which the printing is stopped due to the shortage of toner, the operator supplies toner to the toner hopper as much as possible. The capacity of the toner hopper is several times as large as the capacity of the toner bottle. While toner is being supplied, or while toner is in short supply, in general, it is considered that the normal printing operation can not be conducted in that period. Therefore, it is common that the printing operation is prohibited in the specification of the apparatus. From the viewpoint of control, it is considered that toner can be supplied by the toner supplying mechanism of the prior art while the printing is being conducted. However, consumable goods are generally Supplied while the apparatus is not operated. Therefore, toner supply is prohibited during the printing operation.
In the electrophotographic apparatus of the prior art described above, only one toner shortage signal is used. In accordance with the toner shortage signal, information is reported to the outside of the apparatus, and the printing is stopped and prohibited. Printing is stopped due to the shortage of toner without a previous notice. Therefore, the printing efficiency is lowered when the printing operation is stopped and the apparatus is left as it is. In order to prevent the deterioration of the printing efficiency of the electrophotographic apparatus, it is necessary for the operator to watch the apparatus, which is a heavy burden on him.
The printing operation and toner supply are incompatible with each other. Therefore, only one of them can be carried out. For this reason, the operator must take care of the electrophotographic apparatus until the completion of toner supply at which the next printing can be started. Therefore, a heavy burden is imposed on the operator.